Multiple level methane drainage method

Abstract

A method for collecting methane gas from subterranean formations having a plurality of spaced-apart coal seams containing methane gas includes the steps of drilling a shaft from the earth's surface to a depth sufficient to intersect a plurality of seams containing gas to be collected, excavating a cruciform shaped working area at the selected seams with each of the cruciform shaped working areas communicating with the shaft, and drilling a plurality of boreholes from each of the working areas into the seams and collecting methane gas from the boreholes.

What is claimed is: 
     
       1. A method for collecting gas from subterranean formations having a plurality of spaced-apart seams containing said gas, said method comprising the steps of: drilling a shaft from the earth's surface to a depth sufficient to intersect a plurality of seams containing gas to be collected;   excavating a cruciform-shaped working area at selected seams with each said cruciform-shaped working area communicating with said shaft and said selected seams;   drilling at least one borehole from each of said cruciform-shaped working areas into the seams; and,   collecting gas from said borehole and conducting said gas through said cruciform-shaped working areas and through said shaft to the earth's surface.   
     
     
       2. The method of claim 1, wherein each cruciform shaped working area includes four arms radially disposed from one another at approximately 90 degree intervals and the shaft communicates with each of the cruciform shaped working areas at an intersection of the arms. 
     
     
       3. The method of claim 2, wherein the step of drilling at least one borehole from each of said cruciform shaped working areas includes drilling a generally horizontal borehole outwardly from each of the cruciform shaped working areas. 
     
     
       4. The method of claim 3, wherein the step of drilling at least one borehole from each of said cruciform shaped working areas includes the drilling of a generally horizontal borehole outwardly from ends of the arms of the cruciform shaped working areas. 
     
     
       5. A method for collecting gas from subterranean formations having a plurality of spaced-apart seams containing said gas, said method comprising the steps of: drilling a shaft from the earth's surface to a depth sufficient to intersect a plurality of seams containing gas to be collected;   excavating a cruciform-shaped working area at each seam from which gas is to be collected, each said cruciform-shaped working area communicating with said shaft and said selected seams;   excavating a plurality of drill sites within said cruciform-shaped working area, said drill sites being remote from said shaft;   drilling a plurality of generally horizontal boreholes from each of said drill sites into the seams containing said cruciform-shaped working areas, said generally horizontal boreholes being drilled outwardly from said drill sites in a spaced-apart relationship; and,   collecting gas from said boreholes and conducting said gas through said cruciform-shaped working areas and through said shaft to the earth's surface.   
     
     
       6. The method of claim 1, 2, 3, 4, or 5, wherein at least one of the seams from which gas is to be collected has a thickness of less than about three feet. 
     
     
       7. The method of claim 6 further comprising the step of inserting a liner in each of the boreholes and connecting said liners to a conduit system within the cruciform shaped working areas and shaft for transferring said gas to the earth's surface. 
     
     
       8. The method of claim 5 further comprising the step of drilling a plurality of generally horizontal deflected boreholes from at least one of said generally horizontal boreholes, said deflected boreholes originating and remaining within the coal seam for drawing gas therefrom. 
     
     
       9. The method of claim 8, wherein at least one of the seams from which gas is to be collected has a thickness of less than about three feet. 
     
     
       10. A method for collecting gas from subterranean formations having a plurality of spaced apart seams containing said gas, said method comprising the steps of: drilling a shaft from the earth's surface to a depth sufficient to intersect a plurality of seams containing gas to be collected;   excavating a cruciform shaped working area at selected seams, each cruciform shaped working area including four arms radially disposed from one another at approximately 90 degree intervals, said shaft communicating with each of the cruciform shaped working areas at an intersection of the arms, said cruciform shaped working areas being excavated such that overlying and underlying cruciform shaped working areas have arms disposed at a preselected rotation angle with one another about the shaft;   drilling a plurality of boreholes from each of said cruciform shaped working areas in the seams; and,   collecting gas from said boreholes and conducting said gas through said cruciform shaped working areas and through said shaft to the earth's surface.   
     
     
       11. The method of claim 10, wherein the step of drilling a plurality of boreholes from each of said cruciform shaped working areas includes drilling generally horizontal boreholes outwardly from each of the cruciform shaped working areas. 
     
     
       12. The method of claim 11, wherein the step of drilling a plurality of boreholes from each of said cruciform shaped working areas includes the drilling of generally horizontal boreholes outwardly from ends of the arms of the cruciform shaped working areas. 
     
     
       13. The method of claim 10, 11, or 12, wherein at least one of the seams from which gas is to be collected has a thickness of less than about three feet. 
     
     
       14. The method of claim 13 further comprising the step of inserting a liner in each of the boreholes and connecting said liners to a conduct system within the cruciform shaped working areas and shaft for transferring said gas to the earth's surface. 
     
     
       15. A method for collecting gas from subterranean formations having a plurality of spaced-apart seams containing said gas, said method comprising the steps of: drilling a shaft from the earth's surface to a depth sufficient to intersect a plurality of seams containing gas to be collected;   excavating a cruciform-shaped working area within a plurality of the seams intersected by said shaft, each said cruciform-shaped working area communicating with said shaft and said selected seams;   drilling a plurality of generally horizontal boreholes from each of said cruciform shaped working areas into the seams containing said cruciform shaped working areas, said generally horizontal boreholes being drilled outwardly from said working areas in a spaced-apart relationship; and,   collecting gas from said boreholes and conducting said gas through said cruciform-shaped working areas and through said shaft to the earth's surface.   
     
     
       16. A method for collecting methane gas from subterranean formations having a plurality of spaced apart coal seams containing said methane gas, said coal seams having a thickness of less than three feet, said method comprising the steps of: drilling a shaft from the earth's surface to a depth sufficient to intersect a plurality of coal seems containing methane gas to be collected;   excavating a cruciform shaped working area at each coal seam from which methane gas is to be collected, each said cruciform shaped working area communicating with said shaft;   drilling a plurality of generally horizontal boreholes from each of said cruciform shaped working areas into the coal seams containing said cruciform shaped working areas, said generally horizontal boreholes being drilled outwardly from said cruciform shaped working areas in a spaced apart relationship; and,   collecting methane gas from said boreholes and conducting said methane gas through said cruciform shaped working areas and through said shaft to the earth's surface.   
     
     
       17. A method for collecting methane gas from subterranean formations having a plurality of spaced apart coal seams containing said methane gas, said method comprising the steps of: drilling a shaft from the earth's surface to a depth sufficient to intersect a plurality of coal seems containing methane gas to be collected;   excavating a cruciform shaped working area at selected coal seams, each cruciform shaped working area including four arms radially disposed from one another at approximately 90 degree intervals, said shaft communicating with each of the cruciform shaped working areas at an intersection of the arms, said cruciform shaped working areas being excavated such that overlying and underlying cruciform working areas have arms disposed at an approximately 45 degree rotation angle with one another about the shaft;   drilling a plurality of generally horizontal boreholes from each of said cruciform shaped working areas in the coal seams;   drilling at least one generally horizontal deflected boreholes from at least one of said generally horizontal borehole; and,   collecting methane gas from said boreholes and conducting said gas through said cruciform shaped working areas and through said shaft to the earth's surface.   
     
     
       18. The method of claim 17, wherein at least one of the seams from which gas is to be collected has a thickness of less than about three feet.